Now that the Miiverse has officially ended, Nintendo are seeing to it that games that took advantage of it, get a necessary update that removes the disbanded services functions and in the case of Super Mario Maker, it also removes the old comments on levels as well. The full details can be seen here:

Super Mario Maker for Wii U Ver. 1.47:

Accompanying the ending of the Miiverse service, new comments can no longer be added and existing comments can no longer be viewed on uploaded courses. Courses can still be uploaded, played, and evaluated.

A number of issues have been fixed to make for a pleasant playing experience.

Super Mario Maker for 3DS Ver. 1.04:

A number of issues have been fixed to make for a pleasant playing experience.